1. Field of the Invention
The present invention relates to a diffractive optical element and an optical head using the same. In particular, the present invention relates to a diffractive optical element that emits substantially zero-order diffracted light when light with a wavelength of 0.35 μm to 0.45 μm is incident and emits substantially first-order diffracted light when light with a wavelength of 0.6 μm to 0.7 μm is incident, and an optical head using the same.
2. Description of the Related Art
JP 3047351B discloses a diffractive optical element having a step-wise cross section with four levels, which emits substantially zero-order diffracted light (transmitted light) when light with a red wavelength is incident and emits substantially minus first-order diffracted light when light with an infrared wavelength that is longer than the red wavelength is incident. JP 3047351B also discloses an optical head using the above-mentioned diffractive optical element.
However, even if the technique disclosed in JP 3047351B is applied for both light with the violet wavelength and light with the red wavelength, it is not possible to realize a diffractive optical element that emits substantially zero-order diffracted light (transmitted light) when light with a violet wavelength, which is a shorter wavelength, is incident and emits substantially minus first-order diffracted light when light with a red wavelength, which is longer than the violet wavelength, is incident.